ARM: orion5x: remove legacy mv643xx_eth board setup

With DT support for mv643xx_eth we do not need legacy platform_data
based setup for DT enabled boards. This patch removes eth setup
for all orion5x DT board files.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>